1. Technical Field
The present invention relates to an electrically energizable device for providing heat energy and other combustion products. In particular, the present invention relates to an initiator for an actuatable vehicle occupant protection device, such as an air bag inflator.
2. Description of Related Art
It is known to use an electrically actuatable device known as an initiator, or squib, in various applications. Such devices are used in munitions, detonators, and inflators for vehicle air bags, side curtains, and the like.
A typical initiator includes two electrodes interconnected by a heating element, such as a bridgewire. When an electric current is passed between the electrodes, the heating element generates heat. The heat is used to ignite an output charge in the initiator, typically a quantity of a pyrotechnic material. U.S. Pat. No. 5,939,660 discloses an initiator of this type.
In a vehicle air bag inflator, the initiator does not, itself, produce the inflation fluid needed to inflate the air bag. Rather, the heat generated by the output charge of the initiator effects actuation of an inflation fluid source. In one type of inflator, the initiator ignites a body of gas generating material or an ignitable fluid. In another type of inflator, such as that shown in U.S. Pat. No. 6,227,565 B1, the heat generated by the output charge of the initiator is used to ignite a separate quantity of ignitable material, known as an ignition enhancer. Combustion of the ignition enhancer then effects actuation of the inflation fluid source.
An initiator for an air bag inflator is a small (typically about one centimeter) device that is usually manufactured separately from the other parts of the inflator. The initiator, because it includes an ignitable material, must be made safe for handling when it is not in its intended final use, that is, before it is assembled into the inflator. Thus, stray electric shocks, or electromagnetic radiation, must not be allowed to affect the ignitable material in the initiator. Also, the ignitable material must be handled carefully and, preferably, kept sealed off as much as possible.
The present invention is an apparatus comprising a first assembly and a second assembly. The first assembly comprises a base and an electrically energizable mechanism on the base. The first assembly has a first mounting portion. The second assembly comprises a sealed container and an ignitable material in the container. The container has a first wall portion that is rupturable to enable ignition of the ignitable material. The container has a second wall portion that is rupturable in response to ignition of the ignitable material to enable flow of combustion products of the ignitable material out of the container. The container has a second mounting portion. The first mounting portion of the first assembly is in abutting engagement with the second mounting portion of the second assembly thereby to fix the first assembly for movement with the second assembly. The first wall portion of the container ruptures and the ignitable material in the container ignites in response to energizing of the energizable mechanism.